In the related art, there is known a steam turbine which includes a casing, a shaft body rotatably provided in the inside of the casing, a plurality of turbine vanes fixedly disposed at an inner peripheral portion of the casing, and a plurality of turbine blades radially provided at the shaft body in the downstream sides of the plurality of turbine vanes.
In PTL 1 below, a turbine vane structure ring is constituted by using a turbine vane member having a turbine vane element, an outer shroud element, and an inner shroud element, an outer ring in which a fitting groove is formed in the inner periphery and which is supported on a casing, and an inner ring in which a fitting groove is formed in the outer periphery and which surrounds a rotor.
Specifically, the turbine vane element is annularly retained by inserting and fitting the outer shroud element of each turbine vane member into the fitting groove of the outer ring and also inserting and fitting the inner shroud element into the fitting groove of the inner ring.